1. Field of the Invention
This invention relates generally to a magnetic levitation vehicle system, and more particularly concerns a system for long distance transportation of water by a maglev vehicle such as a maglev train.
2. Description of Related Art
The availability of ample clean water is a major present concern in many regions of the world, and is expected to become an ever greater problem in the decades ahead--in fact, many experts believe it to be the number one problem facing the world. According to a recent U.S. report, a large fraction of the world's population, most of them poor, already lives in a state of water scarcity.
World population is expected to grow to 8.3 billion (mid-range projection) by 2025 AD. This growth, along with increasing industrialization, urbanization and irrigation, will put even more stress on water resources. Many locations in the Western United States are also significantly over-drawing the ground water--in effect, "mining" it, since the aquifer replenishment time is very long. In the Ogalla ("High Plains") aquifer, for example, the water table has already dropped over 100 feet in many locations, due to ground water withdrawals for agriculture. Much of the nation's food comes from this region. Similar overdraft problems are found in California's San Joaquin Valley, Arizona, Nevada, and elsewhere. As the water table drops, ground subsidence often occurs, resulting in damage to structures, cracks, etc. In some locations, ground subsidence of several meters has taken place.
Water demand in the Middle East is even greater than in the Western US, totaling about 200,000 megagallons daily for the countries of Egypt, Iraq, Israel, Jordan, Lebanon, Libya, Oman, Saudi Arabia, Sudan, Syria, Turkey, Yemen, West Bank, and the Gulf States. Demand projections for the year 2000 AD show virtually all of these states, with the exception of Turkey, running a water deficit (in some cases, there is a slight surplus, but it represents a small fraction of total demand).
Once the available ground water is gone, much of the presently irrigated farm land will become unsuitable or uneconomic for food production. In addition, water consumption by domestic and industrial users will have to be severely curtailed, placing a heavy burden on the economy and quality of life.
Such reductions and curtailments appear inevitable in the relatively near future, unless additional supplies of fresh water become available to the western states. Conservation and efficiency improvements can delay the day of reckoning and soften its impact, but it is still inevitable, given the increasing population and the increasing standard of living.
Substantial improvement in reducing water pollution and the large amounts now wasted in inefficient irrigation practices are possible. Such improvements can substantially increase the amounts of useable water in many regions of the world. However, there will be many locations where it would be highly desirable to transport clean water for long distances, e.g., hundreds of miles, if it can be done at an acceptable cost.
Water can also be transported by conventional pipelines and aqueducts. However, for transport distances of hundreds of miles, such systems are very expensive and difficult. FIG. 1 shows the energy cost for pipeline transmission as a function of pipe diameter. The pressure drop and pumping energy scale as pipe diameter.sup.-5, i.e., 1/(pipe diameter) to the 5.sup.th power. As a result of the strong dependence on diameter, for acceptable energy cost, a 300 mile long pipeline system would require a pipe approaching 20 feet in diameter.
Such pipelines are very expensive. Moreover, the total pressure drop of about 1000 psi would require many pumping stations along the 300 mile length. If the maximum P increase that could be handled by the pipeline was approximately 20 psi, on the order of 50 pumping stations, each about 20 feet in diameter would be required, adding additional expense.
Finally, it is likely that any pipeline that traveled hundreds of miles would undergo substantial rises and falls in elevation as it followed the local terrain. If the pipeline elevation were to increase by 20 meters (about 60 feet), an additional 30 psi would have to be injected by a pump. If it were to decrease by approximately 20 meters, approximately 30 psi would have to be removed by a turbo-generator. At a pipe diameter of about 20 feet, the ability to tolerate internal changes in pressure is constrained by stress in the pipe wall. As a result, a water pipeline should travel at near constant elevation, or on a gentle downwards slope (e.g., 1 meter in a kilometer) so that the friction losses compensate for the change in gravitational head.
These problems seriously constrain the capability of large pipelines to carry large quantities of water in rough and hilly terrain. Typically, they either have to be supported on large pier structures like the old Roman aqueducts, or resort to tunnels through hilly or mountainous parts which would be very expensive. A need therefore continues to grow for an effective means for transporting large quantities of clean, fresh water long distances.
Maglev is a new form of transportation in which vehicles are magnetically levitated and propelled at high speeds along a guideway. First generation maglev systems have been developed in Japan and Germany. Implementation of commercial systems is planned between Tokyo and Osaka in Japan, and between Hamburg and Berlin in Germany, shortly after the year 2000.
Vehicles that are levitated magnetically without contacting a support surface encounter reduced friction and vibration problems due to roadbed irregularities. Passenger and freight transport systems utilizing normal permanent magnets or electromagnets have utilized magnetic attraction or repulsion, with the carrier and track held at a set distance through feedback from a gap sensor. One such system, for example, provided for a row of vertical support magnets and another row of lateral guide magnets. Normal motive systems, as well as linear induction motors have also been utilized with such systems for propulsion.
More modern, lighter, more energy efficient electromagnetic inductive levitation and stabilization systems that enable large clearances, typically several inches, have also been proposed for a ground vehicle, utilizing superconducting magnets carried by the vehicle. In one such system, the superconducting magnets interacted with a plurality of arrays of longitudinally extending shorted loops of a non-magnetic metal conductor, such as aluminum, in a guideway. The vehicle was suspended over the guideway by magnetic interaction of the superconducting magnets with the shorted loops in the guideway. The vehicle was supported on wheels when at rest, or when it was started, or operated at transitional speeds below that necessary to suspend the vehicle. Vertical lift was provided by magnetic interaction of the superconducting magnets with coils in the form of individual shorted loops. Horizontal stability was provided by magnetic interaction of the superconducting magnets with coils arranged in a figure 8 shape or in the form of a longitudinally extending series of two vertically spaced, electrically separated loops. The train was propelled by a linear synchronous motor (LSM), in which thrust was obtained by providing AC current to propulsion windings on the ground, which magnetically interacted with, and pushed forward the superconducting magnets located on the car of the train.
Maglev technology has major advantages for the transport of passengers and freight, in that it offers: much lower operating cost and less energy consumption than conventional transport; high speed, weather independent service; convenient, rapid access to nearby stations; efficient intermodal transfer; extremely long service life for vehicles and guideways; and exceptional safety. Because magnetic levitation can provide for efficient and rapid long distance transportation, it would be desirable to provide a maglev transport system to carry large amounts of water, i.e., on the order of 1 billion gallons daily (i.e., 1,000 megagallons per day), for hundreds of miles. The present invention meets these and other needs.